1. Field of the Invention
The present invention relates generally to a wireless charging technology, and more particularly, to a power transmitter and a method for detecting a non-intended object of power reception in a technology for wirelessly transmitting and receiving power, which employs a resonance scheme.
2. Description of the Related Art
A system for wirelessly transmitting power includes a power transmitter and a power receiver. Power is transmitted between a primary coil of the power transmitter and a secondary coil of the power receiver.
There are two types of communication schemes that may be used in the system for wirelessly transmitting power, which has the structure as described above.
The communication schemes include an in-band scheme for performing communication through coils delivering power, and an out-band scheme for performing communication through a communication side separate from the coils delivering the power.
A system for wirelessly transmitting power, which employs an in-band scheme, operates as shown in FIG. 1 and FIG. 2. As shown in FIG. 1 and FIG. 2, a power receiver transmits data by using load modulation, and a power transmitter transmits data by using frequency modulation. In this in-band scheme, power is wirelessly transmitted and communication is performed simultaneously.
In order to sense invalid materials, after authenticating an Identifier (ID), the power transmitter transmits a signal at a particular frequency, and observes a width of a pulse wave. An observed value is compared with a reference value, and material validity is determined based on a result of the comparison.
Before the transmission of power, the power transmitter measures a width of the pulse wave, and acquires a reference value. When power is transmitted, the acquired reference value is used as a reference to determine whether invalid materials have entered.
As described above, when the power transmitter fails to receive an ID authentication frame from the materials sensed when authenticating an ID, it performs a control operation so as to stop the transmission of power to the sensed materials. However, it is difficult to determine that failing to receive the ID authentication frame by the power transmitter is regarded as sensing the invalid receiver or the invalid materials. Also, the measured value is used as the reference value. Accordingly, when the power receiver and the invalid materials are simultaneously placed on a charging deck, it is difficult to detect a non-intended object of power reception.
Moreover, a method for controlling power transmission, which is appropriate in an environment for wirelessly transmitting power to a single object, is described. However, no consideration is given to a method for sensing a non-intended object of power reception in an environment for wirelessly transmitting power to multiple objects.
In the case of an abnormal condition, for example, when invalid materials such as an invalid power receiver and invalid metallic materials are located within a charging area, in the environment for wirelessly transmitting power as described above, there may occur unintended events, such as, for example, failure and overheating, which are caused by power loss/overload.